Aerospace propulsion systems are known in the art. Rockets are propelled using either liquid or solid fuel chemical propulsion or some combination of both. Each system has unique advantages and disadvantages. Liquid fuel chemical propulsion systems can be throttled and are capable of being turned on and off. In addition, the thrust levels can be varied resulting in greater efficiency and flexibility during operation. Liquid propulsion systems, however, generally have a higher mass and require more complex and costly components than do solid rocket systems.
Solid rocket propulsion systems have a lower level of controllability than liquid rocket propulsion systems. Unlike liquid rocket propulsion systems, solid rocket propulsion systems cannot be turned off once lit. Once the propulsion system is turned on, it will continue to burn until all fuel is used up. The inability to be turned off limits the operational envelope and presents a potential safety hazard.
Solid rocket propulsion systems respond more quickly than liquid fuel propulsion systems once turned on. In addition, solid rocket propulsion systems generally have higher performance than liquid fuel propulsion systems, providing a greater thrust/specific impulse per fuel weight. The weight and performance of the fuel is a significant factor for aerospace craft as it is estimated that each additional pound adds $10,000 to the cost of putting a payload into space.
Propulsion systems are usually tailored to meet certain mission requirements and specifications and may have to start and stop a limited number of times. As space applications continue to diversify, scalability in propulsion systems is important and allows rocket builders to more effectively tailor their designs to a given application.
Depending on the mission, liquid propulsion systems also may have inconvenient storage requirements or limited shelf life and may be inconvenient for modular packaging. For example, liquid systems may require the continued cooling for cryogenic fuels with associated insulation and storage tanks while solids would only need a “room temperature” environment.
It is very desirable to have a propulsion system that captures the controllability of liquid propulsion and the high performance of solid propulsion.
It is very desirable to have a propulsion system that is scalable and able to be tailored to a variety of applications, which allows for variable thrust or specific impulse levels.
It is very desirable to have a propulsion system that can be started, stopped and restarted as needed, and which aids in providing high precision performance.
It is very desirable to have a propulsion system with modular design for convenient resupplying, refueling and modifying of ignition/ablation material.
It is further desirable to have a propulsion system that allows multiple systems to be integrated into a single craft.